Step down transformer

[SkeeterFLA]

New to the forum, but I need some assistance. We have European 220v 50Hz single phase as our shore power. We have an outdoor rated mechanical step down transformer (Acme) to get to 110v for U.S. equipment. From the xfmr we are feeding a UPS (APC BE650G1) for equipment back up. Trouble is, the trouble light on the UPS "Building wiring fault" stays on. When we tested the transformer output, the tester indicated "open ground".
Everything is wired correctly and xfmr case is grounded to electrode.
However, if we use an indoor rated step down xfmr, there is no trouble indicator light.
Any ideas?

 

[retirede]

Just a guess: first UPS is checking for a grounded neutral and the first transformer does not have a bond neutral to ground while second one does.

 

[The Great Sarducci]

I second what retirede suggests that the problem may be. Unless your secondary neutral is grounded and bonded to the EGC, it would make sense that the neutral may be floating without a solid 0V reference. I'd definitely start with verifying that your neutral is indeed bonded to ground on the 110V secondary (the 220V primary neutral, if it has one, should not be).

Other than this, I can see no reason why two different transformers of the same PRI/SEC ratings, that are wired the exact same way could possibly make a difference here.

Let us know what you find.